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Titan’s chemical composition from Cassini and ground-based measurements

Presentation #408.03 in the session Titan: Lazy Hazy Days (iPosters).

Published onOct 20, 2022
Titan’s chemical composition from Cassini and ground-based measurements

Titan is one of the most promising bodies in the solar system from the astrobiological perspective in particular, because of its large organic content in the atmosphere and on the surface. These chemical species evolve with time. We performed an analysis using a radiative transfer code of infrared spectra acquired by Cassini/CIRS at high resolution during the Cassini mission and described the temperature and composition variations near the poles and the equator over 13 years [1].

We have also modeled the abundances of the various components in Titan’s atmosphere and searched for some of the trace gases that photochemical models predict but that have not been detected to date.

Cassini’s exploration of Titan provided answers but also raised new questions [1], while several cold cases [2] remain that will constitute major science objectives for future space missions to Titan, like Dragonfly [3], in particular for Titan’s chemical composition, which should be much more complex than what was detected by Cassini-Huygens.

Future in situ measurements will be extremely useful in unveiling this unique complex world. In the meantime, ground-based observations with large telescopes like ALMA, elsewhere in Chile or in Hawaii can help complement the space discoveries. We have obtained observing time at the IRTF with TEXES in 2022 to try and detect some of the trace gases that are expected to be found in Titan’s atmosphere, like

- Cyanopropyne (C4H3N). Its detection could be a by-product of HC3N at 20 micron.

- Acetonitrile (CH3CN), already detected in the millimeter range.

- Acrylonitrile (C3H3N), already observed with ALMA.

- Butene (C4H8), not observed yet, is another hydrocarbon which might result from Titan’s photochemistry.

The detection and monitoring of these molecules would greatly enhance our understanding of the processes in play in the complex atmosphere of Titan, and would provide a valuable input to the Dragonfly future mission to Titan currently in development.


[1] Coustenis, A., 2021. “The Atmosphere of Titan”. In Read, P. (Ed.), Oxford Research Encyclopedia of Planetary Science. Oxford University Press.

[2] Nixon, C. A., et al., 2018. PSS, 155, 50-72.

[3] Barnes, J. et al., 2021. The Plan. Sci. J., 4, 18.

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